1. Field of the Invention
The present invention relates generally to the handling of dialled digits in a wireless telecommunications system, and more particularly to a digit handling system and method for a subscriber terminal of a wireless telecommunications system.
2. Description of the Prior Art
In a typical wireless telecommunications system, a subscriber terminal (ST) may be located at a subscriber""s premises for handling calls to and from that subscriber. One or more lines may be provided from the subscriber terminal for supporting one or more items of telecommunications equipment located at the subscriber""s premises. Further, a central terminal may be provided for controlling a number of subscriber terminals, and in particular for managing calls between a subscriber terminal and other components of a wireless telecommunications network.
Each subscriber terminal communicates with the central terminal via a radio resource. In accordance with known techniques, multiple communication channels may be arranged to utilise the radio resource for the transmission of signals to and from the subscriber terminal. For example, in a xe2x80x9cCode Division Multiple Accessxe2x80x9d (CDMA) system, a radio resource consisting of a particular frequency channel may be partitioned by applying different orthogonal codes to signals to be transmitted on that frequency channel. Signals to which an orthogonal code has been applied can be considered as being transmitted over a corresponding orthogonal communication channel utilising the particular frequency channel. Similarly, in a xe2x80x9cTime Division Multiple Accessxe2x80x9d (TDMA) system, a radio resource consisting of a particular frequency channel can be partitioned in the time domain, such that a number of different signals can be transmitted in different time slots, the time slots forming multiple communication channels utilising the radio resource. As another example, in a xe2x80x9cFrequency Division Multiple Accessxe2x80x9d (FDMA) system, a radio resource consisting of a band of frequencies may be partitioned to form a number of communication channels at particular frequencies, thereby enabling multiple signals to be transmitted over the radio resource.
It is desirable that the item of telecommunications equipment connected to a subscriber terminal is able to behave as though it were connected via a standard wired connection with an exchange (for example, a public switched telephone network (PSTN)), and in particular that the end user does not have to operate the item of telecommunications equipment any differently than he/she would operate the item of telecommunications equipment were it connected directly by a wired connection with the exchange.
In a typical wired system, if a user wishes to make an outgoing call, he/she would cause the item of telecommunications equipment to enter an off-hook state, for example by lifting the handset, the off-hook state would be detected by the exchange, and a real dial tone would then be provided from the exchange to the item of telecommunications equipment. Once the user receives the dial tone, he/she would then be able to enter dialled digits for the destination telephone number, and these would be routed straight through to the exchange.
In current versions of the above described wireless telecommunications system, a similar sequence of events occurs at the item of telecommunications equipment. Hence, when the item of telecommunications equipment enters an off-hook state, this will cause the wireless telecommunications system to establish a link to the exchange including the provision of a communication channel over the radio resource between the central terminal and the subscriber terminal. Once the link is established, the real dial tone is then generated by the exchange, and provided to the item of telecommunications equipment, whereafter the user can enter dialled digits in the usual manner, which are routed straight through to the exchange.
Whilst the above approach enables the item of telecommunications equipment to be operated in an identical manner to that in which it would be operated were the item of telecommunications equipment connected to a conventional wired link, there can be a detectable delay between the item of telecommunications equipment going off-hook and the user being provided with the real dial tone, due to the time taken to establish the link with the exchange via a communication channel of the radio resource. This issue is particularly a concern when the system is operated in a Demand Assignment mode, in which a larger number of STs are associated with the central terminal than the number of traffic-bearing communication channels available on the radio resource. In such a Demand Assignment mode, since a particular ST is not directly associated with a particular communication channel, it typically takes slightly longer to establish the wireless link, due to the extra step of determining an available communication channel over which to place a call.
Accordingly, it would be desirable to provide at technique for more efficiently establishing a call from an item of telecommunications equipment connected to a subscriber terminal, whilst still enabling the item of telecommunications equipment to be operated as though it were connected to a wired network.
Viewed from a first aspect, the present invention provides a digit handling system for a subscriber terminal of a wireless telecommunications system, the subscriber terminal being arranged to have an item of telecommunications equipment connected thereto and being connectable to a central terminal of the wireless telecommunications system via a radio resource to enable a call to be routed between the item of telecommunications equipment and an exchange coupled to the central terminal, the digit handling system comprising: a detector for detecting when the item of telecommunications equipment enters an off-hook state; a dial tone generator for generating a fake dial tone to the item of telecommunications equipment upon detection of the off-hook state; a radio manager, responsive to detection of the off-hook state, for seeking acquisition of a communication channel of the radio resource over which to pass call data; a switching element for controlling the routing of digits through the subscriber terminal, the switching element being arranged to pass to a storage digits received from the item of telecommunications equipment following the detection of the off-hook state; a digit regenerator, responsive to an indication that the communication channel has been acquired, for regenerating each digit stored in the storage and outputting the regenerated digits over the radio resource to the central terminal; the switching element being arranged, upon determination that the storage contains no further digits, to route any further digits received from the item of telecommunications equipment for output over the radio resource to the central terminal without being stored in the storage.
In accordance with the present invention, upon detection of the item of telecommunications equipment entering an off-hook state, a fake dial tone is provided to the item of telecommunications equipment whilst a radio manager seeks acquisition of a communication channel of the radio resource. Since a dial tone has been provided to the item of telecommunications equipment, the user is able to dial digits for the destination telephone number even though the actual link has not yet been established.
Since this approach enables a user to start dialling digits before the link has actually been established, a switching element is provided to pass to a storage any digits received from the item of telecommunications equipment following generation of the fake dial tone. This happens entirely transparently to the end user.
Once the communication channel has been acquired, a digit regenerator then regenerates each digit stored in the storage and outputs the regenerated digits over the radio resource to the central terminal, for forwarding on to the exchange. Whilst this digit regeneration is going on, any additional digits dialled by the user are also stored in the storage. However, at some point, it will be determined that the storage contains no further digits, because the digit regenerator has caught up with the digits already entered by the user, and at this point the switching element is arranged to route any further digits received from the item of telecommunications equipment for output over the radio resource to the central terminal without being stored in the storage.
By the above approach, the user""s perception is that a link is established almost immediately, and accordingly the user can begin dialling the number without delay. The digit handling system is then able to temporarily buffer digits, and regenerate them once the link has been established, with the whole process being transparent to the end user. In addition to increasing the end user""s perception as to the efficiency of the system, this approach can also improve efficiency in real terms, since the digits can typically be regenerated quicker than they are dialled by the user, and because the user can start dialling the digits earlier, the call will often actually be established more quickly than when the earlier described prior art approach is used.
In one embodiment of the invention, the digits are tone dialled digits, and the digit regenerator outputs the regenerated digits over the communication channel acquired by the radio manager with a predetermined delay between each regenerated digit. Hence, each regenerated digit is sent one digit at a time with a predetermined delay (also referred to as an inter-digit pause) between each digit, and this ensures that the digit stream is recreated as if the user had been dialling the regenerated digits directly.
As an alternative to tone dialled digits, the digits may be loop disconnect dialled digits, and in this event the digit regenerator regenerates each stored digit as a digit message and outputs each digit message over a signalling communication channel of the radio resource, with a predetermined delay between each digit message. Hence, any stored loop disconnect dialled digits are sent one digit at a time within a loop disconnect digit message over the radio to the central terminal, and then on to the interface between the wireless telecommunications system and the exchange. The interface will then regenerate the loop disconnect dialled digits towards the exchange; this may be over a message-based protocol (V5.1/V5.2) or CAS depending upon the exchange type. This is in contrast to the handling of tone dialled digits as mentioned earlier, which are regenerated in-band locally within the subscriber terminal.
It will be appreciated by those skilled in the art that the above approach also enables mixed dialling to be handled (e.g. loop disconnect digits followed by tone dialled digits or tone dialled digits followed by loop disconnect digits), and the final digits stream as received by the exchange will be as dialled by the user.
In addition to improving the general efficiency of the dialling process as discussed earlier, further benefits can be realised in accordance with preferred embodiments of the present invention. For example, in preferred embodiments of the present invention, the digit handling system further comprises a number comparator arranged to compare, as each digit is stored in the storage, the number represented by the stored digits with one or more selected numbers, and to issue a match signal to the radio manager if the stored digits match any of the selected numbers. Hence, in accordance with such embodiments of the present invention, the system is able to perform some initial processing based on the digits being buffered in the storage whilst the communication channel is being acquired. It will be appreciated that this initial processing may be used for a variety of purposes. For example, it may be used in determining certain call routing information based on the number being dialled including, for example, radio channel selection, or may be used in connection with call billing applications. However, in preferred embodiments of the present invention, the comparison is used to identify one or more priority numbers that are to be given preferential treatment with regards to the acquisition of a communication channel for calls to those numbers.
In preferred embodiments, upon receipt of the match signal issued by the number comparator, the radio manager is arranged to seek acquisition of a reserved communication channel for the call if the communication channel has not yet been acquired. More particularly, in preferred embodiments, the selected numbers are priority telephone numbers and the reserved communication channel is one of a number of priority channels reserved by the wireless telecommunications system for the handling of priority calls to said priority telephone numbers. Typically, the priority telephone numbers will be definable for each subscriber terminal, for each line of the subscriber terminal, or for a group of subscriber terminals, and may for example be set via a management system of the wireless telecommunications system.
Preferably, upon receipt of the match signal, if the communication channel has already been acquired, the radio manager is arranged to identify that that communication channel should be treated as a reserved communication channel for the duration of the call. Hence, if at the time the match is detected by the number comparator, a communication channel has already been acquired, then in preferred embodiments the radio manager does not seek acquisition of a reserved communication channel, but instead merely treats the communication channel that has already been acquired as a reserved communication channel for the duration of the call. Hence, as an example, the radio manager may identify that communication channel as a reserved communication channel whilst the call is active, to avoid that call being dropped by the wireless telecommunication system for any reason.
In preferred embodiments, the communication channel acquired by the radio manager comprises a downlink communication channel from the central terminal to the subscriber terminal and an uplink communication channel from the subscriber terminal to the central terminal, the switching element being able to independently control the connection of the item of telecommunication equipment to the downlink and uplink communication channels.
It will be appreciated by those skilled in the art that the decision as to when to connect the uplink and downlink communication channels can be controlled in a variety of ways, and preferably is configurable by the management system. For example, the digit regenerator may be arranged to be responsive to detection of a real dial tone signal from the exchange to begin regenerating digits, the exchange being arranged to turn off the real dial tone upon receipt of the first regenerated digit, the switching element being responsive to detection that the real dial tone has been turned off to connect the downlink communication channel to the item of telecommunications equipment. This enables any in-band tones generated by the exchange following turning off of the real dial tone to be passed through to the item of telecommunications equipment.
Further, in preferred embodiments, the switching element is arranged, once the last digit in the storage has been regenerated and the predetermined delay following output of that last digit has expired, to connect the uplink communication channel to the item of telecommunications equipment, after which the switching element is arranged to ensure that no further dialled digits are routed to the storage. Hence, once the digit regenerator has caught up with the digits being dialled by the user, the uplink communication channel is connected to the item of telecommunications equipment, so that any further digits can be handled in the standard manner.
Viewed from a second aspect, the present invention provides a subscriber terminal arranged to have an item of telecommunications equipment connected thereto and being connectable to a central terminal of the wireless telecommunications system via a radio resource to enable a call to be routed between the item of telecommunications equipment and an exchange coupled to the central terminal, the subscriber terminal comprising a digit handling system according to the first aspect of the present invention.
Viewed from a third aspect, the present invention provides a method of handling dialled digits in a subscriber terminal of a wireless telecommunications system, the subscriber terminal being arranged to have an item of telecommunications equipment connected thereto and being connectable to a central terminal of the wireless telecommunications system via a radio resource to enable a call to be routed between the item of telecommunications equipment and an exchange coupled to the central terminal, the method comprising the steps of: detecting when the item of telecommunications equipment enters an off-hook state; generating a fake dial tone to the item of telecommunications equipment upon detection of the off-hook state; responsive to detection of the off-hook state, seeking acquisition of a communication channel of the radio resource over which to pass call data; controlling a switching element to pass to a storage digits received from the item of telecommunications equipment following the detection of the off-hook state; responsive to an indication that the communication channel has been acquired, regenerating each digit stored in the storage and outputting the regenerated digits over the radio resource to the central terminal; upon determination that the storage contains no further digits, controlling the switching element to route any further digits received from the item of telecommunications equipment for output over the radio resource to the central terminal without being stored in the storage.
Viewed from a fourth aspect, the present invention provides a computer program operable to configure a subscriber terminal of a wireless telecommunications system to perform a method in accordance with the third aspect of the present invention. The present invention also relates to a carrier medium comprising such a computer program.